feat: add verify_ssl option for SMTP connections (#105)

feat: add verify_ssl option for SMTP connections

Author: Wh1isper

README.md

@@ -63,23 +63,24 @@ You can also configure the email server using environment variables, which is pa
 
 #### Available Environment Variables
 
-| Variable                                      | Description                                      | Default       | Required |
-| --------------------------------------------- | ------------------------------------------------ | ------------- | -------- |
-| `MCP_EMAIL_SERVER_ACCOUNT_NAME`               | Account identifier                               | `"default"`   | No       |
-| `MCP_EMAIL_SERVER_FULL_NAME`                  | Display name                                     | Email prefix  | No       |
-| `MCP_EMAIL_SERVER_EMAIL_ADDRESS`              | Email address                                    | -             | Yes      |
-| `MCP_EMAIL_SERVER_USER_NAME`                  | Login username                                   | Same as email | No       |
-| `MCP_EMAIL_SERVER_PASSWORD`                   | Email password                                   | -             | Yes      |
-| `MCP_EMAIL_SERVER_IMAP_HOST`                  | IMAP server host                                 | -             | Yes      |
-| `MCP_EMAIL_SERVER_IMAP_PORT`                  | IMAP server port                                 | `993`         | No       |
-| `MCP_EMAIL_SERVER_IMAP_SSL`                   | Enable IMAP SSL                                  | `true`        | No       |
-| `MCP_EMAIL_SERVER_SMTP_HOST`                  | SMTP server host                                 | -             | Yes      |
-| `MCP_EMAIL_SERVER_SMTP_PORT`                  | SMTP server port                                 | `465`         | No       |
-| `MCP_EMAIL_SERVER_SMTP_SSL`                   | Enable SMTP SSL                                  | `true`        | No       |
-| `MCP_EMAIL_SERVER_SMTP_START_SSL`             | Enable STARTTLS                                  | `false`       | No       |
-| `MCP_EMAIL_SERVER_ENABLE_ATTACHMENT_DOWNLOAD` | Enable attachment download                       | `false`       | No       |
-| `MCP_EMAIL_SERVER_SAVE_TO_SENT`               | Save sent emails to IMAP Sent folder             | `true`        | No       |
-| `MCP_EMAIL_SERVER_SENT_FOLDER_NAME`           | Custom Sent folder name (auto-detect if not set) | -             | No       |
+| Variable                                      | Description                                       | Default       | Required |
+| --------------------------------------------- | ------------------------------------------------- | ------------- | -------- |
+| `MCP_EMAIL_SERVER_ACCOUNT_NAME`               | Account identifier                                | `"default"`   | No       |
+| `MCP_EMAIL_SERVER_FULL_NAME`                  | Display name                                      | Email prefix  | No       |
+| `MCP_EMAIL_SERVER_EMAIL_ADDRESS`              | Email address                                     | -             | Yes      |
+| `MCP_EMAIL_SERVER_USER_NAME`                  | Login username                                    | Same as email | No       |
+| `MCP_EMAIL_SERVER_PASSWORD`                   | Email password                                    | -             | Yes      |
+| `MCP_EMAIL_SERVER_IMAP_HOST`                  | IMAP server host                                  | -             | Yes      |
+| `MCP_EMAIL_SERVER_IMAP_PORT`                  | IMAP server port                                  | `993`         | No       |
+| `MCP_EMAIL_SERVER_IMAP_SSL`                   | Enable IMAP SSL                                   | `true`        | No       |
+| `MCP_EMAIL_SERVER_SMTP_HOST`                  | SMTP server host                                  | -             | Yes      |
+| `MCP_EMAIL_SERVER_SMTP_PORT`                  | SMTP server port                                  | `465`         | No       |
+| `MCP_EMAIL_SERVER_SMTP_SSL`                   | Enable SMTP SSL                                   | `true`        | No       |
+| `MCP_EMAIL_SERVER_SMTP_START_SSL`             | Enable STARTTLS                                   | `false`       | No       |
+| `MCP_EMAIL_SERVER_SMTP_VERIFY_SSL`            | Verify SSL certificates (disable for self-signed) | `true`        | No       |
+| `MCP_EMAIL_SERVER_ENABLE_ATTACHMENT_DOWNLOAD` | Enable attachment download                        | `false`       | No       |
+| `MCP_EMAIL_SERVER_SAVE_TO_SENT`               | Save sent emails to IMAP Sent folder              | `true`        | No       |
+| `MCP_EMAIL_SERVER_SENT_FOLDER_NAME`           | Custom Sent folder name (auto-detect if not set)  | -             | No       |
 
 ### Enabling Attachment Downloads
 
@@ -150,6 +151,35 @@ sent_folder_name = "INBOX.Sent"
 
 **To disable saving to Sent folder**, set `MCP_EMAIL_SERVER_SAVE_TO_SENT=false` or `save_to_sent = false` in your TOML config.
 
+### Self-Signed Certificates (e.g., ProtonMail Bridge)
+
+If you're using a local mail server with self-signed certificates (like ProtonMail Bridge), you'll need to disable SSL certificate verification:
+
+```json
+{
+  "mcpServers": {
+    "zerolib-email": {
+      "command": "uvx",
+      "args": ["mcp-email-server@latest", "stdio"],
+      "env": {
+        "MCP_EMAIL_SERVER_SMTP_VERIFY_SSL": "false"
+      }
+    }
+  }
+}
+```
+
+Or in TOML configuration:
+
+```toml
+[[emails]]
+account_name = "protonmail"
+# ... other settings ...
+
+[emails.outgoing]
+verify_ssl = false
+```
+
 For separate IMAP/SMTP credentials, you can also use:
 
 - `MCP_EMAIL_SERVER_IMAP_USER_NAME` / `MCP_EMAIL_SERVER_IMAP_PASSWORD`

mcp_email_server/config.py

@@ -29,6 +29,7 @@ class EmailServer(BaseModel):
     port: int
     use_ssl: bool = True  # Usually port 465
     start_ssl: bool = False  # Usually port 587
+    verify_ssl: bool = True  # Set to False for self-signed certificates (e.g., ProtonMail Bridge)
 
     def masked(self) -> EmailServer:
         return self.model_copy(update={"password": "********"})
@@ -96,6 +97,7 @@ def init(
         smtp_port: int = 465,
         smtp_ssl: bool = True,
         smtp_start_ssl: bool = False,
+        smtp_verify_ssl: bool = True,
         smtp_user_name: str | None = None,
         smtp_password: str | None = None,
         save_to_sent: bool = True,
@@ -119,6 +121,7 @@ def init(
                 port=smtp_port,
                 use_ssl=smtp_ssl,
                 start_ssl=smtp_start_ssl,
+                verify_ssl=smtp_verify_ssl,
             ),
             save_to_sent=save_to_sent,
             sent_folder_name=sent_folder_name,
@@ -141,6 +144,7 @@ def from_env(cls) -> EmailSettings | None:
         - MCP_EMAIL_SERVER_SMTP_PORT (default: 465)
         - MCP_EMAIL_SERVER_SMTP_SSL (default: true)
         - MCP_EMAIL_SERVER_SMTP_START_SSL (default: false)
+        - MCP_EMAIL_SERVER_SMTP_VERIFY_SSL (default: true)
         - MCP_EMAIL_SERVER_SAVE_TO_SENT (default: true)
         - MCP_EMAIL_SERVER_SENT_FOLDER_NAME (default: auto-detect)
         """
@@ -183,6 +187,7 @@ def parse_bool(value: str | None, default: bool = True) -> bool:
                 smtp_port=int(os.getenv("MCP_EMAIL_SERVER_SMTP_PORT", "465")),
                 smtp_ssl=parse_bool(os.getenv("MCP_EMAIL_SERVER_SMTP_SSL"), True),
                 smtp_start_ssl=parse_bool(os.getenv("MCP_EMAIL_SERVER_SMTP_START_SSL"), False),
+                smtp_verify_ssl=parse_bool(os.getenv("MCP_EMAIL_SERVER_SMTP_VERIFY_SSL"), True),
                 smtp_user_name=os.getenv("MCP_EMAIL_SERVER_SMTP_USER_NAME", user_name),
                 smtp_password=os.getenv("MCP_EMAIL_SERVER_SMTP_PASSWORD", password),
                 imap_user_name=os.getenv("MCP_EMAIL_SERVER_IMAP_USER_NAME", user_name),

mcp_email_server/emails/classic.py

@@ -1,5 +1,6 @@
 import email.utils
 import mimetypes
+import ssl
 from collections.abc import AsyncGenerator
 from datetime import datetime, timezone
 from email.header import Header
@@ -72,6 +73,20 @@ async def _send_imap_id(imap: aioimaplib.IMAP4 | aioimaplib.IMAP4_SSL) -> None:
         logger.warning(f"IMAP ID command failed: {e!s}")
 
 
+def _create_smtp_ssl_context(verify_ssl: bool) -> ssl.SSLContext | None:
+    """Create SSL context for SMTP connections.
+
+    Returns None for default verification, or permissive context
+    for self-signed certificates when verify_ssl=False.
+    """
+    if verify_ssl:
+        return None
+    ctx = ssl.create_default_context()
+    ctx.check_hostname = False
+    ctx.verify_mode = ssl.CERT_NONE
+    return ctx
+
+
 class EmailClient:
     def __init__(self, email_server: EmailServer, sender: str | None = None):
         self.email_server = email_server
@@ -81,6 +96,11 @@ def __init__(self, email_server: EmailServer, sender: str | None = None):
 
         self.smtp_use_tls = self.email_server.use_ssl
         self.smtp_start_tls = self.email_server.start_ssl
+        self.smtp_verify_ssl = self.email_server.verify_ssl
+
+    def _get_smtp_ssl_context(self) -> ssl.SSLContext | None:
+        """Get SSL context for SMTP connections based on verify_ssl setting."""
+        return _create_smtp_ssl_context(self.smtp_verify_ssl)
 
     def _parse_email_data(self, raw_email: bytes, email_id: str | None = None) -> dict[str, Any]:  # noqa: C901
         """Parse raw email data into a structured dictionary."""
@@ -630,6 +650,7 @@ async def send_email(
             port=self.email_server.port,
             start_tls=self.smtp_start_tls,
             use_tls=self.smtp_use_tls,
+            tls_context=self._get_smtp_ssl_context(),
         ) as smtp:
             await smtp.login(self.email_server.user_name, self.email_server.password)
 

tests/test_email_client.py

@@ -1,13 +1,14 @@
 import asyncio
 import email
+import ssl
 from datetime import datetime, timezone
 from email.mime.text import MIMEText
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
 
 from mcp_email_server.config import EmailServer
-from mcp_email_server.emails.classic import EmailClient
+from mcp_email_server.emails.classic import EmailClient, _create_smtp_ssl_context
 
 
 @pytest.fixture
@@ -354,3 +355,85 @@ async def test_send_email_without_reply_headers(self, email_client):
             msg = call_args[0][0]
             assert "In-Reply-To" not in msg
             assert "References" not in msg
+
+
+class TestSmtpSslContext:
+    """Tests for SMTP SSL context creation."""
+
+    def test_create_smtp_ssl_context_with_verification(self):
+        """When verify_ssl=True, should return None (use default verification)."""
+        result = _create_smtp_ssl_context(verify_ssl=True)
+        assert result is None
+
+    def test_create_smtp_ssl_context_without_verification(self):
+        """When verify_ssl=False, should return permissive SSL context."""
+        result = _create_smtp_ssl_context(verify_ssl=False)
+
+        assert result is not None
+        assert isinstance(result, ssl.SSLContext)
+        assert result.check_hostname is False
+        assert result.verify_mode == ssl.CERT_NONE
+
+    def test_email_client_get_smtp_ssl_context_default(self):
+        """EmailClient should use verify_ssl from EmailServer (default True)."""
+        server = EmailServer(
+            user_name="test",
+            password="test",
+            host="smtp.example.com",
+            port=587,
+        )
+        client = EmailClient(server)
+
+        # Default verify_ssl is True, so should return None
+        assert client.smtp_verify_ssl is True
+        assert client._get_smtp_ssl_context() is None
+
+    def test_email_client_get_smtp_ssl_context_disabled(self):
+        """EmailClient should return permissive context when verify_ssl=False."""
+        server = EmailServer(
+            user_name="test",
+            password="test",
+            host="smtp.example.com",
+            port=587,
+            verify_ssl=False,
+        )
+        client = EmailClient(server)
+
+        assert client.smtp_verify_ssl is False
+        ctx = client._get_smtp_ssl_context()
+        assert ctx is not None
+        assert ctx.check_hostname is False
+        assert ctx.verify_mode == ssl.CERT_NONE
+
+    @pytest.mark.asyncio
+    async def test_send_email_passes_tls_context(self):
+        """send_email should pass tls_context to SMTP connection."""
+        server = EmailServer(
+            user_name="test",
+            password="test",
+            host="smtp.example.com",
+            port=587,
+            verify_ssl=False,
+        )
+        client = EmailClient(server, sender="test@example.com")
+
+        mock_smtp = AsyncMock()
+        mock_smtp.__aenter__.return_value = mock_smtp
+        mock_smtp.__aexit__.return_value = None
+        mock_smtp.login = AsyncMock()
+        mock_smtp.send_message = AsyncMock()
+
+        with patch("aiosmtplib.SMTP", return_value=mock_smtp) as mock_smtp_class:
+            await client.send_email(
+                recipients=["recipient@example.com"],
+                subject="Test",
+                body="Body",
+            )
+
+            # Verify SMTP was called with tls_context
+            call_kwargs = mock_smtp_class.call_args.kwargs
+            assert "tls_context" in call_kwargs
+            ctx = call_kwargs["tls_context"]
+            assert ctx is not None
+            assert ctx.check_hostname is False
+            assert ctx.verify_mode == ssl.CERT_NONE